Eric
Got your PM. I always collimate at the start of the night with the scope at roughly 45deg, that way I figure I minimise any movement that may occur as it moves through its range.
Take the locking knobs and chuck 'em away, completely useless if you have strong springs. I have used Bobs Knobs springs and seem to work OK.
As I only use my scope for visual work, I have not found geting too pernicky over collimation does at lot of good, quite frankly I could spend a lot more time, effort and money getting it just so, and probably couldn't tell the difference in the image anyways!
My time is much better spent looking at DSOs, drooling over scopes, or posting bits of largely useless info on IIS!
While a 12" needs to be well collimated and needs checking every night,
spending more than 1-2 minutes per session is a waste of time IMHO.
Malcolm